x86: prevent stale state of c1e_mask across CPU offline/online

Impact: hang which happens across CPU offline/online on AMD C1E systems.

When a CPU goes offline then the corresponding bit in the broadcast
mask is cleared. For AMD C1E enabled CPUs we do not reenable the
broadcast when the CPU comes online again as we do not clear the
corresponding bit in the c1e_mask, which keeps track which CPUs
have been switched to broadcast already. So on those !$@#& machines
we never switch back to broadcasting after a CPU offline/online cycle.

Clear the bit when the CPU plays dead.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/process.c

@@ -246,16 +246,21 @@ static int __cpuinit check_c1e_idle(const struct cpuinfo_x86 *c)
 	return 1;
 }
 
+static cpumask_t c1e_mask = CPU_MASK_NONE;
+static int c1e_detected;
+
+void c1e_remove_cpu(int cpu)
+{
+	cpu_clear(cpu, c1e_mask);
+}
+
 /*
  * C1E aware idle routine. We check for C1E active in the interrupt
  * pending message MSR. If we detect C1E, then we handle it the same
  * way as C3 power states (local apic timer and TSC stop)
  */
 static void c1e_idle(void)
 {
-	static cpumask_t c1e_mask = CPU_MASK_NONE;
-	static int c1e_detected;
-
 	if (need_resched())
 		return;
 

arch/x86/kernel/process_32.c

@@ -88,6 +88,7 @@ static void cpu_exit_clear(void)
 	cpu_clear(cpu, cpu_callin_map);
 
 	numa_remove_cpu(cpu);
+	c1e_remove_cpu(cpu);
 }
 
 /* We don't actually take CPU down, just spin without interrupts. */

arch/x86/kernel/process_64.c

@@ -93,6 +93,8 @@ DECLARE_PER_CPU(int, cpu_state);
 static inline void play_dead(void)
 {
 	idle_task_exit();
+	c1e_remove_cpu(raw_smp_processor_id());
+
 	mb();
 	/* Ack it */
 	__get_cpu_var(cpu_state) = CPU_DEAD;

include/asm-x86/idle.h

@@ -10,4 +10,6 @@ void idle_notifier_register(struct notifier_block *n);
 void enter_idle(void);
 void exit_idle(void);
 
+void c1e_remove_cpu(int cpu);
+
 #endif